I’m an advocate of diets relatively rich in protein and low in carbohydrate. Not uncommonly when I addressing an audience regarding this, someone will ask me about the Atkins’ diet and my opinion of it. Digging a bit it usually turns out that the individual is thinking that I’m advocating an Atkins-like diet, and we all know that these sort of diets are bad news for the heart, so it seems like I’m advocating a diet that is bad for the heart. Given my qualified support of the Atkins diet, and the generally unhealthy reputation this diet has, then questions of this nature are valid and pertinent.
However, what is the evidence that the Atkins or similar diet is bad for the heart? Some of this notion is connected with the concept that the Atkins diet is high in fat, particularly saturated fat that ’causes heart disease’. The thing is, though, there is no good evidence that saturated fat causes heart disease. See here for more on this.
Another common cause for concern regarding the Atkins diet is the amount of protein in it. Some people have come to the conclusion that protein is somehow bad for the heart. I’m not sure where this notion originated. It might be part of the anti-Atkins propaganda that includes the telling us that protein is bad for the kidneys and bones too. While protein intake may need to be limited by those with compromised kidney function, there is no evidence that it is damaging to individuals with normal kidney function (the vast majority of us). And studies suggest that higher protein intakes are actually associated with improved bone health.
But what about the relationship between protein and heart health? One recent study that has shed some light on this looked at the relationship between protein levels in the diet and blood pressure [1]. This study, conducted in Japan, found that the higher animal protein intake was, the lower blood pressure was found to be too.
This is not the only study to have found that higher protein intakes are associated with lower blood pressure [2].
Higher protein diets have also, generally speaking, been found to bring about favourable changes in the other markers for risk factors for heart disease including lowered levels of blood fats known as triglycerides and raised levels of ‘healthy’ HDL cholesterol.
One of the ways protein might exert its apparent beneficial effects on the cardiovascular system is because it displaces carbohydrate from the diet (the more protein people eat, the less carb they tend to eat). And this is important because carbs are the primary drivers of insulin secretion, one effect of which is ‘sodium retention’. One potential consequence of retaining sodium in the body is elevated blood pressure. Elevated levels of insulin, sometimes as part of a condition known as ‘metabolic syndrome’, are associated with elevated levels of triglyceride and lower HDL levels. It can also lead to ‘insulin resistance’ and type 2 diabetes, which are risk factors for heart disease.
But even before insulin levels start to be raised, spikes in blood sugar from eating an excess of carbs can lead to a variety of effects believed to enhance heart disease risk including increases in ‘oxidative stress’ (free radical damage), inflammation (a key underlying process in heart disease), protein glycation (glucose ‘bonding’ to proteins in the body and damaging them), and coagulation (essentially, making the blood ‘stickier’ and more likely to clot).
I was partly triggered to writing about this today because recently the Journal of the American Dietetic Association published a case-study which claims that a man’s heart disease was induced, and quickly at that, by the Atkins diet [3]. Look, anything is possible, but the evidence (for those that care to look) strongly suggests that such a diet, if anything, actually reduces the risk of heart disease overall.
References:
1. Umesawa M, et al. Relations between protein intake and blood pressure in Japanese men and women: the Circulatory Risk in Communities Study (CIRCS). Am J Clin Nutr 2009;90: 377-384
2. Hu FB. Protein, body weight, and cardiovascular health. American Journal of Clinical Nutrition 2005;82(1); 242S-247S.
3. Barnett TD, et al. Development of symptomatic cardiovascular disease after self-reported adherence to the Atkins Diet. J Am Diet Assoc. 2009;109:1263-1265.
